A couple with a small child walk past a propaganda poster promoting the single child policy in Beijing. Photograph: Adrian Bradshaw/EPA

China's single child policy was once a source of pride to government planners, with slogans reflecting strict family planning laws emblazoned on buildings across the country.

But reminders of the policy's harshest excesses are being scrubbed away in an effort to create a softer message, with officials phasing out older, threatening slogans in favour of more upbeat ones.

According to the People's Daily, the aim is to "make family planning work keep pace with the times and go deep among the masses".

The single child policy is unlikely to be rescinded soon, because doing so would cause uproar among those denied second children. But it has frayed at the edges, with multiple groups, including ethnic minorities and the mothers of disabled children, being allowed a second child.

Family planners are also seeking subtler approaches, such as more teenage sex education.

Slogans from the early days of the policy, which was launched in 1979, stressed punishments for couples who had unplanned pregnancies. Typical examples included: "If sterilisation or abortion demands are rejected, houses will be toppled, cows confiscated".

These slogans conveyed "coldness, constraint and even threats. They easily caused resentment in people and led to social tension", the People's Daily said.

A report entitled Outdoor Propaganda for Population and Family Planning has called for fresh slogans, the newspaper said. Work to scrub away remnants of the old ones began in 2007. Recent slogans will also be reviewed for suitability.

Newer slogans tend to promote the benefits of having fewer children or advocate gender equality, for instance: "Lower fertility, better quality; boys and girls are all treasures". A current slogan warns: "Mistreatment and abandonment of baby girls is strictly prohibited."

An unintended consequence of the single child policy has been widespread, though illegal, sex-selective abortion, and infanticide.

Forced abortions continue to take place, human rights groups say. Chen Guangcheng, a lawyer, remains under house arrest in Shandong province for campaigning on behalf on local women. Police have prevented foreign journalists from visiting him.

Wall slogans are no longer the main method of propaganda, because sex information is widely available online. Recent experiments with sex lessons for primary school children, using anatomically explicit dolls, caused controversy.

Teenage sex education is increasingly accepted and focuses on relationship-building, making limiting family size a more easily digestible message.

Propagandists have been busy modernising and softening other slogans and imagery felt to be out of date and potentially counterproductive prior to the March annual meeting of the National People's Congress.

Photos of the model soldier Lei Feng, a Maoist youth hero, have emerged showing him astride a motorbike, sporting a fashionably floppy haircut.

Lei was a model soldier who died in 1962, aged 22, when a telegraph pole fell on him. Lei was known for selfless service to his comrades. Chairman Mao coined the slogan "learn from Lei Feng". A national Lei Feng day started in 1963 on 5 March.

Exhortations to learn from Lei continue to be used. A more cynical catchphrase is "I'm not Lei Feng", used to reject, or mock, a request the speaker finds unreasonable. But debate has emerged about whether China's youth can still relate to him.

Past role models were also usually depicted as "overly self-controlled and lofty to the extent of being like gods", the paper said.

The "de-deification of Lei Feng will promote his appeal," according to the Global Times newspaper.